Tire failure is the most frequent cause of downtime for industrial construction equipment. This is especially the case for the heavy equipment operated adjacent to buildings under construction. There is a substantial amount of sharp debris such as nails, rods, wire, etc. on the ground which cause punctures of the tires. The downtime of the equipment effects the schedule of the operations and can cause a cascade of events delaying the project. Equipment operators, at high pay, sit idly by awaiting repair of the tire or rental of another piece of equipment. Service to repair heavy equipment tires is expensive.
Another source of unreliability is the prevalence of accidents due to tipping or rollover of heavy construction equipment. This again causes downtime and also results in expense for equipment repair and medical and leave requirements for injured personnel. All of these add to the insurance costs of the contractor.
The construction industry cannot afford any unnecessary costs. There is increasing competition, both from domestic and foreign sources. Inflation in costs of material and labor cause a spiral of upward costs difficult to predict and not capable of being controlled by the contractor unless he prepurchases all materials for the job. The industry is generally plagued with inefficient operations.
There are ways to prevent deflation of tires from punctures. One way is to fill the tire with a foamable preparation. These materials are expensive, can contain flammable or hazardous materials and are permanent. They are sensitive to contamination and require delay while the foam cures. Any voids can cause the foamed unit to break. Once installed they cannot be removed. They also are sticky and gooey and difficult to handle and cleanup. They also have low specific gravity and do not provide sufficient ballast effect.
About twenty years ago, aqueous suspensions of clays were used as tire sealants and ballasts. Certain substances such as barite, attapulgite, bentonite and the like became hydrated to a gel-like state in water. The viscous gel can seal small tire punctures. The clay suspensions have a high density and provide ballast. They also can be removed. Different amounts can be added to different tires depending on the situation.
The tire sealing clay suspensions were not completely stable and could separate resulting in tires leaking through the punctures. The size of puncture that could be sealed was limited. Furthermore, since the suspension were aqueous based and could freeze, there use was limited to locations with warmer climates.
It was attempted to depress the freezing point of the suspensions by using sea water which contains calcium and magnesium ions instead of fresh water to form the tire sealant. However, the suspension made with sea water was thinner and did not seal as well. Also calcium chloride is 20 times more toxic than sodium chloride and can corrode metal parts and degrade rubber tires and tubes.
It was then attempted to depress the freezing point of the tire sealant suspension by the addition of alkylene glycol such as ethylene glycol or propylene glycol. Though the freezing point was lowered, the suspension was destabilized and the tires leaked tire sealant through the punctures.